Chemical Kinetics for Reaction of 5-Nitro-1H-benzo[d]imidazole to Produce 6- Nitro-1H-benzo[d]imidazole and Calculation of Heat Capacity of Activation

The kinetics and mechanism of the reaction of 5-nitro-1h-benzo[d] imidazole to produce 6-nitro-1h-benzo[d] imidazole is studied by employing hybrid meta-density functional theory. mpwblk/6-31+g** level calculations are carried out to obtain energies, to optimize the geometries of all stationary points along the pes, and also to determine the harmonic vibrational frequencies. two transition states (ts1 and ts2) and a chemically-energized intermediate (int) are involved along the calculated potential energy surface. rrkm-tst is used to compute the temperature dependence of the rate constants, which are determined using nonlinear least-squares fitting at 273-1000 k. the arrhenius plot for all reactions is shown positive temperature dependence. thermodynamic parameters are also used to determine the stability and the extent of spontaneity of the reaction. the self-consistent reaction field (scrf) associated with dft-based energy, optimization, and frequency calculations are used to model systems in solution and to compare them with the rate constants in the gas and solvent (water) phases. the variations of activation energy in the temperature range (273-1000 k) are determined in the gas and solvent phases. the heat capacity of activation of reactions (∂ea/∂t) are also reported which is temperature dependent and is significant in low temperature.